In view of numerous factors such as higher energy prices and environmental concerns, the production of value-added gaseous products from lower-fuel-value carbonaceous feedstocks, such as petroleum coke and coal, is receiving renewed attention. The catalytic gasification of such materials to produce methane and other value-added gases is disclosed, for example, in U.S. Pat. No. 3,828,474, U.S. Pat. No. 3,998,607, U.S. Pat. No. 4,057,512, U.S. Pat. No. 4,092,125, U.S. Pat. No. 4,094,650, U.S. Pat. No. 4,204,843, U.S. Pat. No. 4,468,231, U.S. Pat. No. 4,500,323, U.S. Pat. No. 4,541,841, U.S. Pat. No. 4,551,155, U.S. Pat. No. 4,558,027, U.S. Pat. No. 4,606,105, U.S. Pat. No. 4,617,027, U.S. Pat. No. 4,609,456, U.S. Pat. No. 5,017,282, U.S. Pat. No. 5,055,181, U.S. Pat. No. 6,187,465, U.S. Pat. No. 6,790,430, U.S. Pat. No. 6,894,183, U.S. Pat. No. 6,955,695, US2003/0167961A1, US2006/0265953A1, US2007/000177A1, US2007/083072A1, US2007/0277437A1 and GB1599932.
Synthesis gas (i.e., a gas mixture having predominant quantities of CO and H2) is typically used as a feedstock for other processes, for example processes used to make lower alcohols and ethers as well as hydrocarbonaceous products such as Fischer-Tropsch diesel fuel and synthetic crude oil (syncrude). Synthesis gas can be formed from lower-fuel value feedstocks using, for example, gasification processes. For example, in one such process a carbonaceous feedstock is gasified non-catalytically by partial oxidation by a mixture of oxygen and steam; about a third of the feedstock is burned in the process to provide heat and pressure, making this process relatively energy-inefficient. In other such processes, catalytic gasification is followed by one or more cryogenic separations to separate the catalytic gasification product gas into methane and CO/H2 fractions. These processes can be disadvantaged in that they are relatively energy-intensive. Accordingly, processes are needed which can more efficiently form syngas-derived products from lower-fuel-value carbonaceous feedstocks.